Calculate the initial size of bubbles forming above a porous distributor plate for a bed wherein $u_o=35c\frac{m}{s}$ and $u_{mf}=3c\frac{m}{s}.$

Calculate the initial size of bubbles forming in the bed of Prob. $4$ if the porous plate distributor is replaced by a perforated plate with a square array of $3-mm$ holes spaced $1cm$ apart.